Forming gaseous sulfides and sulfidation therewith



suitable manner.

Patented Jan. 17, 1950 FORMING GASEOUB SULFIDES AND SULFIDATION THEREWITH Hubert A. Shabaker, Media, Pa assigns:- to

Houdry Process Corporation, Wilmington, Del a corporation of Delaware No Drawing. Application December 4, 1047, Serial No. 789.611

17 Claims. (01. 252-450) The present invention relates to the preparation and use of sulfiding gases and particularly to chemical modification of iron-containing clays and earths by reaction with sulfiding gases.

In a copending application, Serial No. 844,423, filed Jointly in the names of myself, George Alexander Mills, and Ruth C. Denison, now U. S. Patent No. 2,466,048, issued April 5, 1949, there are disclosed methodsv for improving clays and preparing catalysts including the steps of treating the clay. with H18 at elevated temperature and subsequently acid leachin the sulfided clay. The use of carbon disulfide at temperatures above about 1300 F. as the sulilding agent for this purpose is described in our later filed application, Serial No. 681,426, new U. 8. Patent No. 2, 406,- 052. a

Certain advantages are described in my application Serial No. 774,439 resulting from the use of a diluted sulfiding gas in an essentially inert hot gaseous carrier in sulfiding of clays, particularly for the preparation of improved catalysts and contact masses.

In accordance with the present invention, an active gaseous sulfide in an essentially inert carrier gas is prepared ,directly by contacting a heated gas substantially free from uncombined oxygen and containing minor amounts of H: and/or CO and added free sulfur, with a natural absorptive hydrosilicate of aluminum serving as a surface combustion mass, such as a clay or earth. In the presence of the combustion mass the H2 and/or C combineswlth S readily, forming Has and/or CS: respectively, together with intermediate gaseous sulfides (e.g. COS) These active gaseous sulfides formed, when at a sumciently high temperature, react with iron compounds present in the absorptive mass employed converting the same to iron sulfides; which may thenbe removed by acid washing or in other I By thus forming the active sulfiding gas from relatively inexpensive sulfur and available reducing gas, important savings in cost of active sulfiding gases are provided.

Instead of employing as the surface combustion mass, the clay or earth containing ii'onrompounds which is to be subjected to sulfidation by a the sulfide gases formed, a separate contact mass may be employed to further the reactions forming the sulfiding gas, for instance the combination of hydrogen with sulfur, and the sulfide gases thus formed brought directly into contact with the iron-containing clay or earth for the acquired conversion of the iron compounds there- In the preparationof catalytic contact masses from clay by methods, including sulfidation, it is necessary to maintain the temperature below that at which the clay sinters or begins to shrink rapidly. In the case of most montmorillonite clays, including sub-'bentonites, the maximum temperature to be employed, therefore, is at about 1500-1550" F., while with other clays includinB those containing chiefiy kaolinite or a related clay mineral, somewhat higher temperatures are permitted, as up to 1600-1850' 1''.

The gas composition prepared in accordance with the invention may be controlled so as to contain within limits any desired proportion of active gaseous or vaporimble sulfide such as H28 or CS1, depending upon the quantity of sulfur added to the starting gas and the content of components present therein reactive with sulfur under the conditions. No advantage is seen, however, for the purpose of the present invention, in having present an amount of sulfur in excess of that required to react with components of the starting gas.. On the other hand. it may be desirable in many instances to employ an amount of 8 less than that required for reaction with components of the starting gas, so as to leave unreacted a small portion of the components reactive with sulfur.

The starting gas may be of almost any composition so long as it contains hydrogen and/or carbon monoxide and is essentially free from constituents interfering with or incompatible with the gaseous or readily vaporizable sulfides to be formed. Thus free oxygen is contraindicated, since the same would consume part of the added 8 in the formation of oxygenated sulfur compounds. If the ultimate sulfiding gas mixture is to be employed in the preparation of catalytically active clays, the amount of water present during contact with the clay should be reduced to a minimum by drying the starting gas and by avoiding compounds reactive under the conditions to form water in an amount in excess of about 2 mol percent of the total treating gas composition.

A convenien-'.- source of starting gas is a comon such as a fiue gas obtainable by controlled combustion of a hydrocarbon fuel in air to essentially use up all of the free oxygen content.

The combustion can be controlled so that the oxygen is substantially entirely consumed and the flue gas contains appreciable quantities of H: and/or 00. From the controlled burning of a hydrocarbon such as propane, for instance, substantially oxygen-free mixtures may be obtained predominating in nitrogen and containing 0.5 to 3.0% H: and from 1 to 4.5% CO. The amount oi C; concomitantly formed will vary from about 11 to 13%: the balance of 85 to 81.5% being subsiantiaily all nitrogen, all on a water free basis. By appropriate control of combustion, mixtures containing larger amounts of Hz and/or CO can also be obtained with concomitant formation of less CO2 and N2.

By the incomplete combustion of a hydrocarbon gas or mixture of such gases, residual unburned hydrocarbons present in the mixture will react with added sulfur to form additional quane tiiies of desired sulfiding gas. For instance, methane directly reacts with S to form hydrogen sulfide and carbon disulfide.

For the preparation of improved catalysts, in accordance with my joint application Serial No. 644,423, hereinbefore referred to, the sulfidation of theclay should be carried out at temperatures in the order of about 1200 F. and above. With certain clays employed industrially, as in the preparation of ceramic wares, where reduction of iron to the extent obtained with the indicated high temperature sulflding treatment is not required, lower operating temperatures for sulfldation can be employed, as in the order 01' 400-600 F. Here too. however, more eflicient operation is had at higher temperatures up to the point that the clay irreversibly loses its plasticity or is otherwise impaired in properties for the particular purpose for which it is desired to be employed.

The following is an example of a practical op eration in accordance with the invention for the preparation of a catalytic contact mass of low iron content directly utilizing the sulfiding gas formed in situ. Propane is burned in the presence of air under conditions to furnish a flue gas composed of (after drying) 1.3 mol per cent hydrogen, 1.6 mol per cent carbon monoxide, 12.7 mol per cent carbon dioxide and 84.4 mol per cent nitrogen by volume. To the gas heated to 1350 F. about mol per cent of free sulfur is added in finely in pelleted form. The total volume of gas employed is that suflicient to provide Hrs and CS2 in about 4 times the equivalent theoretically required to react with the iron present in the clay about 2% as R203) to convert the same to iron sulfide.

The iron sulfide thus formed may be readily removed from the clay, for instance by acid leaching as described in application Serial No. 644.423 heretofore referred to. Thus, the sulflded clay is treated with dilute aqueous hvdrochloric acid of -20% concentration at room temperature for 24 or more hours, then washed and dried. Alternatively, a separate contact mass such as kaolin clay could be employed for the initial preparation of the dilute sulfiding gas and the latter contacted with the iron-containing clay to be treated.

Although CO: has an adverse effect on the suliidation of clay by CS: or H28. if the content of active sulflding gas such as CS2 or H28 in the treating composition is sufficient to provide at least 3 to 4 times the stoichiometric equivalent of the iron content of the clay, 10 to CO2 in the gas composition can be tolerated and the suliided clays easily leached to obtain clay prodnets of desired residual low iron content. As a general rule, during initial heating and sulildation of the clay with dilute mixtures of H28 and/or CS: as with treating gas containing 10% or less by weight of active sulfiding agent, the volume ratio of COa/HaS plus CS: should not exceed about 10. It will be seen that the composition of the treating gas in the above example is well within these limits.

In the above example, the amount of sulfur added to the hot flue gas is about the theoretical quantity calculated to react with the total CO and H2 content of the flue gas. Too large an I excess of free sulfur should be avoided. since deposition 'of the same in the clay may interfere with subsequent acid leaching. The amount of sulfur added, however, should be at least sumcient to furnish an amnut of CS2 plus Ha-S calculated to react with an of the iron present in the clay and preferably several times that amount. The total quantity and rate of introduction of the treating gas should be controlled to bring the clay to required sulfidingtemperature and to maintain the same at such temperature during the sulflding action. For effective sulfidation of the clay in the preparation of improved catalysts of low iron content, temperatures above 1200 F. and preferably in the range of 1350-1450" F. should be employed. Based on air, it was found that about 1000 to 1300 volumes of gas are required to heat one volume of pelleted clay, weighing about 45 pounds per cubic foot. from room temperature to about 1400 F. This number of volumes of treating gas to clay is generally about suflicient for bringing the clay to preferred sulfidation temperatures and for'eflecting sulfidation, using flue gas of various compositions or other gaseous compositions predominating in nitrogen.

Possible variat onsin the composition of the starting gas which are readily obtainable, are shown in the following tabulation:

such as H28 and CS2, with each of the above starting gases. and the consequent composition of the diluted treating gas, will be determined by the quantity of added sulfur, up to the stoichiometric amount. Thus the above compositions will theoretically yield treating gases containing from 1.0 to 9.0 mol per cent of active gaseous sulfides,

calculated as H28 and CS2, or constituting ap-.

proximately from 2 to 13% by weight of the total treating gas.

A gas comprising essentially Na-i-Hz can be obtained by controlled combustion of H2 in air under conditions that the amount of H2 is in desired excess of that necessary to completely react with the oxygen in the air,

By the methods of the present invention, it will. accordingly be seen, important advantages in the.

efficiency and economy of operations involving the sulfldation of clays and'mineral earths are D1707.

access:

need in addition to those derived by the use of the diluted sulfiding gas. The production of the treating gas can be readily controlled to obtain 7 directly active sulflding gas in a heated carrier gas of desired temperature and composition and without waste of the active sulfiding agent thus ob tained and utilized. Because of the decreased handling requirements, these gaseous sulfides can 8. The process. in accordance with claim 6- wherein said flue gas is a product of controlled combustion of a hydrocarbon gas in air and is be employed at the high temperatures of treatment described. with minimum corrosive effect on the treating apparatus. In addition, separate heating of the1clay to required sulfidationtem: perature is rendered unnecessary, since the contained sensible heat of the diluted-sulfiding gas as produced. can be beneficially utilized for maintaining the clay at the desired temperature during sulfidation. Moreover, the advantages resulting from the use of the diluted -sulfiding gas. as pointed out in my copending application referred to, also obtain here. including substantial uniformity of sulfidation of the clay and the improved facility of iron removal. as by acid leaching, of the formed iron sulfide, with consequent consistent production of low iron products, such as catalysts. oi desired quality and uniformity.

Obviously many modifications and variations of the invention as hereinbefore set forth may be made without departing from the spirit and scope thereof and therefore only such limitations should be imposed as are indicated in the appended claims.

I claim as my invention:

1. A process of directly producing a sulfiding gas mixture comprising an active gaseous sulfide in an essentially inert gaseous carrier. which comprises bringing together elemental sulfur and a gaseous reactant capable of direct combination with sulfur, at reaction temperature and in the presence of a natural absorptive hydrosilicate of aluminum. to form a sulfide which is gaseous at the reaction temperature; said reactant being selected from the group consisting of hydrogen, carbon monoxide, and mixtures of these, and being contained as a minor constituent in an essentially inert heated gaseous carrier, and said elemental sulfur being suspended in said gaseous carrier in finely divided form.

2. The process in accordance with claim 1 wherein said gaseous'reactant comprises hydrogen.

8. The process in accordance with claim 1 wherein said gaseous reactant comprises carbon monoxide.

4. The process in accordance with claim 1 wherein said natural hydrosilicate of aluminum consists essentially of a clay containing iron compounds which iron compounds. are thus sulflded by the gaseous sulfide formed in situ.

5. The process in accordance with claim 4 wherein said sulfidation of the clay containing iron compounds is effected at a temperature not less than 1200" F. and short of that at which rapid shrinkage of the clay will result.

6. The process of sulfiding natural absorptive hydrosilicate of aluminum containing iron compounds with dilute sulfiding gas at elevated temperature, which comprises contacting with said hydrosilicate a heated flue gas containing a minor proportion of free hydrogen and having added elemental sulfur suspended in said flue gas, said flue gas being at a temperature sufiiciently high to effect chemical combination of hydrogen and sulfur in the presence of said hydrosilicate; thereby effecting conversion of iron compounds contained in said hydrosilicate to iron sulfide; said iii) employed'in. dried state containing 0.5 to 3 mol 9 per cent hydrogen. 1 to 4.5 mol per cent carbon monoxide, 11 to 13% carbon dioxide, the remainder ofthe composition of the flue gas alone consisting essentially of nitrogen. T

9. The process of preparing catalytically active contact masses of low iron content which comprises contacting a clay containing iron compounds with a diluted sulfiding gas. at atemperature ofat least 1200 F and below that at which sintering of the clay results, and thereafter leaching the iron sulfide formed with dilute acid; said diluted sulfiding'gas being composed of minor amounts of hydrogen sulfide and carbon disulfide carried in an essentially inert carrier gas, and said sulfiding gas being produced by reacting with elemental sulfur and in the presence of clay, hydrogen and carbon monoxide contained in a heated gaseous mixture predominating in inert gas.

10. The process in accordance with claim 9 wherein said heated gaseous mixture predominating in inert gas is produced by controlled combustion in air of a hydrocarbon gas under conditions efiecting substantially complete consumption of oxygen in the air.

11. The method of. preparing from iron-containing clays catalytically active masses of improved properties, which comprises heating such a clay to a temperature of 12001550 F. by contact with a hot gas mixture comprising essentially inert carrier gas and minor quantities of active gaseous sulfide and maintaining the clay in com I 12. The process in accordance with claim 11 wherein the quantity of active gaseous sulfide present in the gas mixture employed is at least 3 times the stoichiometric equivalent of the iron content of the clay subjected to sulfidation.

13. The process in accordance with claim 12 wherein said dried flue gas comprises 0.5 to 3% hydrogen, 1 to 4.5% carbon monoxide, 11 to 13% carbon dioxide, the remainder of the composition being substantially all nitrogen, and the quantity of added elemental sulfur is not more than the stoichiometric amount required for reaction with the hydrogen and carbon monoxide.

14. The process in accordance with claim 11 wherein said iron containing clay is a pelleted acid-activated montmorillonite.

15. The process of claim 11 wherein said hot gas mixture contains not more than 10% by weight of active gaseous sulfide.

16. In a process for sulfidation of iron-conv taining clays, the improvement which comprises g by weight 0! the gas mixture oi active Iulflding gas but in amounts at least several times the stoichiometric equivalent or the iron content of the clay, said heating and suliidation medium being obtained by combustion of a hydrocarbon gas in air under conditions to consume substantially the entire oxygen content of the air. and contacting with clay the obtained iiue gas together with added elemental suiiur at a temperature of at least 1200 I". but below that causing substantial incipient fusion of the clay.

17. The process of preparing hydrocarbon conversion catalysts of improved properties 1mm iron-containing clays, which comprises the steps 01' reacting in the presence or a combustion mess and at elevated temperatures elemental sulfur and hydrogen contained in an essentially inert carrier gas to form a treating gas comprising hydrogen suiiide and unreacted components or said carrier gas, the proportions being so selected that to 3,314,353

smear the time iormed treating ges predominates in unreeeted components or the initial carrier gas, introducing the formed treatlns as into contact with on iron-containing clay at a temperature of 5 it 1M 1200 F. but below that eflecting substantial incipient iusion oi the clay. to transiorm iron compounds present in the clay to iron sulfide, cooling the thus suiiided clay, and leaching the cooled city to remove iron sulfide.

HUBER! A. BHABAKER.

REFERENCES CITED The ioiiowing references are of record in the file of this potent:

UNI'IED STATES PATENTS Number Name Date 1,851,155 Ikeds Sept. '7, 1920 1,566,894 Bindschedier et ai. 15, 1925 Maude ct si. Sept. 17, 1940 

6. THE PROCESS OF SULFIDING NATURAL ABSORPTIVE HYDROSILICATE OF ALUMINIUM CONTAINING IRON COMPOUNDS WITH DILUTE SULFIDING GAS AT ELEVATED TEMPERATURE, WHICH COMPRISES CONTACTING WITH SAID HYDROSILICATE A HEATED FLUE GAS CONTAINING A MINOR PROPORTION OF FREE HYDROGEN AND HAVING ADDED ELEMENTAL SULFUR SUSPENDED IN SAID FLUE GAS, SAID FLUE GAS BEING AT A TEMPERATURE SUFFICIENTLY HIGH TO EFFECT CHEMICAL COMBINATION OF HYDROGEN AND SULFUR IN THE PRESENCE OF SAID HYDROSILICATE; THEREBY EFFECTING CONVERSION OF IRON COMPOUNDS CONTAINED IN SAID HYDROSILICATE TO IRON SULFIDE; SAID FLUE GAS BEING SUBSTANTIALLY FREE FROM UNCOMBINED OXYGEN. 